Characterizing fault-controlled fluid-CO₂ migration in West Bohemia/Vogtland through seismic and magnetotelluric joint inversion

The West Bohemia/Vogtland region, situated at the intersection of the Saxothuringian, Teplá-Barrandian, and Moldanubian Units, is characterized by mantle-derived CO2 emissions, earthquake swarms, and Quaternary volcanism. To investigate the crustal structure and fluid-CO2 migration, we applied a joint inversion of body-wave and magnetotelluric data, producing three-dimensional models of P-wave velocity (Vp), S-wave velocity (Vs), and electrical resistivity (ρ). The joint inversion algorithm constrained geophysical models using variation of information (VI) coupling and updated earthquake locations via the double-difference method.

The results reveal linearly aligned patches of low Vp, high Vp/Vs, and low ρ along the Počátky-Plesná Fault Zone in the upper crust, indicating hydraulically conductive zones under critical stress. At ~10 km depth beneath the Nový Kostel focal zone, a prominent anomaly characterized by low Vp, high Vp/Vs, and high ρ suggests a fluid-CO₂ system under high pressure, likely explaining the triggering mechanisms of earthquake swarms. Near the Hartoušov Mofette Field, anomalies with low Vp, low Vp/Vs, and high ρ suggest a gas-dominated fracture network in the upper crust. These findings provide new insights into the interaction of tectonics, magmatism, and crustal fluids in this geodynamically active region.